1. Field of the Invention
The present invention relates to an ink jet printing apparatus that performs printing by ejecting ink to print media.
2. Description of the Related Art
Ink jet printing apparatuses have been prevailing which perform printing by moving a print head while ejecting ink onto print media. These ink jet printing apparatuses have been desired to achieve improved print quality because they are sometimes used to print images or the like which are picked up with a digital camera or the like. A factor preventing the ink jet printing apparatus from achieving improved print quality is inappropriate ejection that may occur when the first droplets of ink are ejected from ejection ports after a long interval. The inappropriate ejection may occur if the ink jet printing apparatus has not been used for a long time and when a volatile component of ink vaporizes from ejection ports that communicate with nozzles, increasing the viscosity of the ink. Then, the ejection may be disabled or an impact position may deviate from the correct one depending on the level of the viscosity. This may degrade print quality. With this regard, the ink ejection condition can be recovered by removing the higher-viscosity ink located in the vicinity of the ejection ports. Accordingly, to allow the first droplets to be smoothly ejected, the conventional technique performs preliminary ejection separate from printing ink ejection to eject ink to a position off a print medium to remove the higher-viscosity ink. In this case, the print head, comprising the ejection ports, moves to a dedicated place where the preliminary ejection is to be performed and after the preliminary ejection, returns to a printing position to perform printing again.
However, for the ink jet printing apparatus, there are now growing demands not only for the improved print quality but also for improved weatherability, increased print speed, and the like. To meet these demands, it is desirable to employ ink characterized by improved weatherability and high color developing capability. However, the ink characterized by improved weatherability and high color developing capability tends to have a high viscosity. Accordingly, its use is disadvantageous in allowing the first droplets to be smoothly ejected. Further, when high-viscosity ink is used, the preliminary ejection may be more frequently performed during printing in order to allow the first droplets to be smoothly ejected. However, frequent preliminary ejections require correspondingly frequent movements to the place for preliminary ejection, reducing the print speed. Furthermore, frequent preliminary ejections increase the amount of waste ink ejected during the preliminary ejections instead of being used for printing. Moreover, an increased amount of waste ink requires a waste ink absorber having a large capacity enough to accommodate the waste ink.